The present invention relates generally to corrosion inhibitors, and more particularly, at least in some embodiments, to corrosion inhibitors comprising reaction products of an aldehyde with a thiol and/or an amine functionalized ring structures, and methods of using such inhibitors in subterranean applications.
Metals such as carbon steel alloys, copper alloys, chrome alloys, and nickel alloys are commonly used in subterranean application equipment (such as in drilling pipes and mixing tanks) and installations (such as gravel pack screens, tubing, and casings). Oftentimes, these metals are subjected to corrosive fluids during subterranean operations.
One such corrosive fluid is an acidizing fluid. Subterranean hydrocarbon-containing formations penetrated by well bores are commonly treated with aqueous acid solutions to stimulate the production of hydrocarbons therefrom. One such treatment known as “acidizing” involves the introduction of an aqueous acid solution into the subterranean formation under pressure so that the acid solution flows through the pore spaces of the formation. The acid solution reacts with acid soluble materials contained in the formation thereby increasing the size of the pore spaces and the permeability of the formation. Another production stimulation treatment known as “fracture-acidizing” involves the formation of one or more fractures in the formation and the introduction of an aqueous acid solution into the fractures to etch the fracture faces whereby flow channels are formed when the fractures close. The aqueous acid solution also enlarges the pore spaces in the fracture faces in the formation. Some commonly used acids include hydrochloric acid, hydrofluoric acid, acetic acid, formic acid, citric acid, ethylene diamine tetra acetic acid (“EDTA”), and combinations thereof.
In carrying out acidizing and fracture-acidizing treatments in wells and other similar treatments using aqueous acid solutions, the corrosion of metal tubular goods, pumps, and other equipment is often a problem. The expense associated with repairing or replacing corrosion damaged metal tubular goods and equipment can be very high. In a well treatment utilizing an aqueous acid solution, the corrosion of metal surfaces in tubular goods and equipment results in at least the partial neutralization of the aqueous acid solution before it reacts with acid-soluble materials in the subterranean formation to be treated. Also, the presence of dissolved metals in the aqueous acid solution can bring about the precipitation of insoluble sludge when the aqueous acid solution contacts crude oil which can in turn severely damage the permeability of the subterranean formation being treated.
A variety of metal corrosion inhibiting formulations for use in aqueous acid solutions have been developed and used. Many of such corrosion inhibiting formulations have included quaternary ammonium compounds as essential components, particularly in high temperature applications. However, problems have been associated with the use of quaternary ammonium compounds in that they are generally highly toxic to aquatic organisms. Further, the quaternary ammonium compounds that achieve high degrees of metal corrosion protection at high temperatures are those that have relatively high molecular weights and high degrees of aromaticity. Those quaternary ammonium compounds are not readily available commercially and are very expensive to produce. Subterranean applications now require alloys of increasing corrosion resistance and strength. These increasing demands arise from factors including: deep wells that involve higher temperatures and pressures; enhanced recovery methods such as steam or carbon dioxide (CO2) injection; increased tube stresses especially offshore; and corrosive well constituents including: hydrogen sulfide (H2S), CO2 and chlorides. Materials selection is especially critical for sour conditions, which are those having H2S present. Sour well environments are highly toxic and extremely corrosive to traditional carbon steel oil and gas alloys. In some sour environments, corrosion can be controlled by using inhibitors along with carbon steel tubulars. The inhibitors, however, involve continuing high cost and are often unreliable at high temperatures. Additionally, conventional inhibitors are generally not effective in sour conditions because the organic portion of the inhibitor is believed to react with the H2S, which decreases the performance of the inhibitor. Furthermore, in sour conditions, copper and antimony-based intensifiers will precipitate out of solution.